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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer
摘要： The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol% or with 62.2/29.4/8.4 mol% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content.
关键词： P(VDF-TrFE-CFE) terpolymer,Curie transition,relaxor-ferroelectric polymer,ferroelectric and paraelectric phases
更新于2025-09-23 15:22:29
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Nanoconfinement-Induced Giant Electrocaloric Effect in Ferroelectric Polymer Nanowire Array Integrated with Aluminum Oxide Membrane to Exhibit Record Cooling Power Density
摘要： The electrocaloric effect (ECE) offers a unique mechanism to realize environmentally friendly and highly efficient solid-state cooling that completely differs from the conventional vapor-compression refrigeration. Here a new class of hybrid films composed of ferroelectric polymer nanowire array and anodic aluminum oxide (AAO) membrane is reported, which displays pronounced ECE driven by relatively low electric fields. Under confinement and orientation of AAO channels on the crystallization of the polymer, the polymer nanowire array shows substantially enhanced ECE that is about three times that of the corresponding thin films. Simultaneously, the integrated AAO membrane forms thermally conducting channels for the polymer nanowires, enabling the efficient transfer of cooling energy and operation of the EC materials under high frequencies, which are unattainable based on the currently available EC structures. Consequently, the integrated polymer nanowire–AAO hybrid film exhibits the state-of-the-art cooling power density, outperforming the current ferroelectric polymers, ceramics, and composites. This work opens a new route for the development of scalable, high-performance EC materials for next-generation refrigeration.
关键词： electrocaloric effect,nanoconfinement,cooling power density,heat transfer,ferroelectric polymer
更新于2025-09-23 15:22:29
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Controlled doping of graphene by impurity charge compensation via a polarized ferroelectric polymer
摘要： A simple technique of doping graphene by manipulating adsorbed impurity charges is presented. Using a field effect transistor configuration, controlled polarization of a ferroelectric polymer gate is used to compensate and neutralize charges of one type. The uncompensated charges of the opposite type then dope graphene. Both n- and p-type doping are possible by this method, which is non-destructive and reversible. We observe a change in n-type dopant concentration of 8 × 1012 cm?2 and a change in electron mobility of 650%. The electron and hole mobilities are inversely proportional to the impurity concentration, as predicted by theory. Selective doping of graphene can be achieved using this method by patterning gate electrodes at strategic locations and programming them independently. Such charge control without introducing hard junctions, therefore, permits seamless integration of multiple devices on a continuous graphene film.
关键词： ferroelectric polymer,doping,graphene,charge compensation,field effect transistor
更新于2025-09-23 15:21:01
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Polarization Properties and Polarization Depth Profiles of (Cd:Zn)S/P(VDF-TrFE) Composite Films in Dependence of Optical Excitation
摘要： The influence of optical excitation intensity on the electrical, ferroelectric and pyroelectric properties of ferroelectric-semiconductor-composites was investigated. For this purpose, composite thin films consisting of poly(vinylidene fluoride-co-trifluoroethylene) and 10 vol % (Cd:Zn)S particles with a thickness of 34 μm were fabricated. The samples were used to measure the absolute pyrocoefficient and to determine the relative pyroelectric depth profile using Laser Intensity Modulated Method. It was shown that a polarization of the samples without an optical excitation at the utilized relatively small peak-to-peak voltages could not be verified by the Sawyer–Tower circuit and the measurement setup of the pyroelectric coefficient, respectively. Both remanent polarization and pyroelectric coefficients increased with increasing optical excitation intensity during poling as well as increasing peak-to-peak voltage. The pyrocoefficient shows a temporal decay in the first hours after poling. The specific heat and thermal conductivity or the thermal diffusivity are required for the calibration of the pyroelectric depth profile. Rule of mixture and photo-acoustic investigations proved that the thermal properties of the utilized composites do not differ significantly from those of the pristine polymer. Based on the pyroelectric depth profile which is proportional to the polarization profile, the existing “three phase model” has been extended to generate a replacement circuit diagram, explaining the local polarization due to the optical excitation dependency for both local resistivity and local field strength.
关键词： composite,optical excitation,ferroelectric polymer,semiconductor
更新于2025-09-19 17:15:36
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Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
摘要： Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
关键词： epitaxy,epitaxial interaction,semiconducting polymer,graphene,crystal interaction,transition-metal dichalcogenide,ferroelectric polymer,two-dimensional materials
更新于2025-09-19 17:13:59
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Orientation Dependence of Power Generation on Piezoelectric Energy Harvesting Using Stretched Ferroelectric Polymer Films
摘要： The piezoelectric vibration energy harvesters were fabricated by using uniaxially stretched poly (vinylidene difluoride/trifluoroethylene) copolymer (P(VDF/TrFE)) film, and the relationship between piezoelectric power generation and molecular orientation was investigated. The molecular orientation in the stretched P(VDF/TrFE) films was evaluated with polarized Fourier transfer infrared (FT-IR) spectra measurement. In stretched films, the main-chains of P(VDF/TrFE) were aligned along the stretching direction. The piezoelectric properties and the electric power generation of stretched P(VDF/TrFE) films were strongly depended on their molecular orientation, measuring by cantilever-type energy harvesters. The piezoelectric coefficient(e) and output power observed in the energy harvester with the film stretched in the longitudinal direction of cantilever were 16.9 mC/m2 and 222 nW, respectively. These values were approximately 2.1 and 3.5 times these of the unstretched elements.
关键词： P(VDF/TrFE),piezoelectric,molecular orientation,energy harvesting,ferroelectric polymer
更新于2025-09-10 09:29:36